1. Field of Invention
The present invention relates to a laser annealing apparatus having a plurality of optical systems to generate a plurality of laser beams.
2. Discussion of Related Art
FIG. 1 shows a schematic structure of a laser annealing apparatus according to a related art. Referring to FIG. 1, a laser annealing apparatus comprises a laser oscillator 11 generating and providing a laser beam, an optical system 15 processing energy and profile of the laser beam provided by the laser oscillator 11 to be applied to a sample directly, and a laser annealing chamber (not shown in the drawing) in which various steps take place, such as directly using the laser beam processed by the optical system 15 for the sample.
The description of the operation of the laser annealing apparatus having the above constitution is as follows. (The work of irradiating a laser beam to an amorphous silicon layer is taken as an example to explain the operations of the annealing apparatus in the following description.)
First, an initial laser beam is generated by the laser oscillator 11 and is passed to the optical system 15. The initial laser beam is a non-processed and crude laser beam. The optical system 15 processes the initial laser beam into a laser beam 100 having a predetermined shaped profile and a predetermined magnitude of energy for a sample irradiation. A sample, such as an amorphous silicon layer 18 in the laser annealing chamber, is irradiated with the laser beam processed by the optical system 15.
In this case, the laser beam is applied to the amorphous silicon layer 18 with a predetermined repetition rate and the amorphous silicon layer 18 moves to one direction consecutively. Accordingly, the whole amorphous silicon layer 18 is scanned by the laser beam. The part of the amorphous silicon layer 18 which was scanned by the laser beam becomes a crystalline silicon layer due to the crystallization of the silicon.
In FIG. 1, a mirror 12 establishes a path of the laser beam. The amorphous silicon layer 18 is formed on a substrate 19.
The laser beam of the laser annealing apparatus in the related art is patterned to have a line pattern for scanning an amorphous silicon layer of a large area. A profile of the laser beam of a line pattern in the laser annealing apparatus according to related art is shown in FIG. 2.
FIG. 2 shows a plan and cross-section of a profile of a laser beam having a line pattern in a laser annealing apparatus of related art. Unfortunately, the annealing apparatus of the related art has a limit to elongate the length of the laser beam due to a single optical system. Some of the laser annealing apparatus according to a related art are unable to have a substrate of a large area irradiated with a laser beam by a single scan. Accordingly, it is difficult for the laser annealing apparatus to complete a laser scanning process as intended.
Accordingly, the present invention is directed to a laser annealing apparatus that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
The object of the present invention is to provide a laser annealing apparatus which has at least two optical systems and processes a laser beam of a wide width by having the laser beams overlap one another, wherein the laser beams are supplied from each optical system.
Additional features and advantages of the invention will be set forth in the description which follows and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a laser annealing apparatus for use with a laser beam for irradiating a sample material comprises: at least one beam splitter arranged in the path of the laser beam, the beam splitter separating the laser beam into a plurality of split laser beams; and a plurality of optical systems arranged in the paths of the plurality of split laser beams, each optical system transforming an associated split laser beam into an elongated beam for irradiating the sample material, wherein the plurality of optical systems are arranged to align elongated beams in a length direction. Preferably, the beam splitter has a penetration ratio which is substantially equivalent to a reflection ratio to split the laser beam to at least two split laser beams having substantially identical energy density. The laser beam is produced from a laser oscillator, and the sample material is disposed in a laser annealing chamber.
According to one aspect of the present invention, the plurality of optical systems are arranged to allow the elongated beam from each optical system to partially overlap with each other in the length direction for irradiation the sample material. Alternatively, the plurality of optical systems may be arranged to allow the elongated beam from each optical system to be separated by a predetermined space in the length direction.
Each one of the plurality of optical systems is configured to shape the edges of the respective laser beam to have a sloped energy density region. Alternatively, each one of the plurality of optical systems may be configured to shape the edges of the respective laser beam to have a stepped energy density region. The plurality of optical systems are arranged to allow the elongated beam from each optical system to partially overlap with each other in the length direction, wherein the overlapped region of the elongated beams has substantially identical energy density as non-overlapped regions.
A method of irradiating a sample material using a laser annealing apparatus comprises the steps of: generating a laser beam; arranging at least one beam splitter in a path of the laser beam, the beam splitter separating the laser beam from the laser oscillator into a plurality of split laser beams; and arranging a plurality of optical systems in the paths of the plurality of split laser beams, each optical system transforming an associated split laser beam into an elongated beam for irradiating the sample material, wherein the plurality of optical systems are arranged to align elongated beams in a length direction.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.